The invention concerns a method for manufacturing a cast product comprising an aluminum friction bearing alloy having portions of zinc, copper, magnesium, silicon and lead, as well as the product itself. A friction bearing alloy of this kind is e.g. Alzn4.5CuMgSiPb which the applicant has been producing for some time under the trade name KS 961. This friction bearing alloy is distinguished by its high stability under load. It has not been possible up to now to increase the lead content to a satisfactory degree for improving the emergency running properties, i.e. to increase resistance to scuffing, since with lead contents of more than 1 mass %, phase separation occurs in the liquid melt in the form of a precipitation of a liquid lead phase. This separation for higher lead content of the aluminum alloy friction bearing prevents formation of finely distributed lead precipitates. It has not been previously possible to produce a superior quality friction bearing material of this kind. EP 0 440 275 A1 proposes a continuous casting method for an aluminum alloy which can comprise one or more of the following components: 1 to 50 mass % lead, 3 to 50 mass % bismuth and 15 to 50 mass % indium and additionally one or more of the components: 0.1 to 20 mass % silicon, 0.1 to 20 mass % tin, 0.1 to 10 mass % zinc, 0.1 to 5 mass % magnesium, 0.1 to 5 mass % copper, 0.05 to 3 weights iron, 0.05 to 3 mass % manganese, 0.05 to 3 mass % nickel and 0.01 to 0.3 mass % titanium, wherein the billet is chilled with direct cooling water at a rate of 700 K/s. This procedure is intended to prevent formation of large-volume minority phase precipitates during the time period between arrival at the segregation temperature and solidification of the matrix metal. It has, however, turned out that direct water cooling of the solidifying billet is associated with large temporal and spatial fluctuations in the cooling rate, leading to inhomogeneities in the cast product. Process stability required for series production cannot be achieved in a reproducible fashion. Moreover, due to the very high cooling rate, there is the considerable danger that cracks are formed in the cast product.
It is therefore the underlying purpose of the present invention to improve the emergency running properties of the above-mentioned aluminum alloy friction bearing.